Selected Correspondence:
Letter 56 (52) Spinoza to Hugo Boxel.

Dear Sir, -Your letter, which I received
yesterday, was most welcome to me, both because
I wanted to hear news of you, and also because
it shows that you have not utterly forgotten me.
Although some might think it a bad omen, that
ghosts are the cause of your writing to me, I,
on the contrary, can discern a deeper meaning in
the circumstance; I see that not only truths,
but also things trifling and imaginary may be of
use to me.

However, let us defer the question, whether
ghosts are delusions and imaginary, for I see
that not only denial of them, but even doubt
about them seems very singular to you, as to
one who has been convinced by the numerous
histories related by men of to-day and the
ancients. The great esteem and honour, in which
I have always held and still hold you, does not
suffer me to contradict you, still
less to humour you. The middle course, which I shall adopt, is
to beg you to be kind enough to select from the numerous
stories which you have read, one or two of those least open to
doubt, and most clearly demonstrating the existence of ghosts.
For, to confess the truth, I have never read a trustworthy
author, who clearly showed that there are such things. Up to
the present time I do not know what they are, and no one has
ever been able to tell me. Yet it is evident, that in the case of a
thing so clearly shown by experience we ought to know what it
is; otherwise we shall have great difficulty in gathering from
histories that ghosts exist. We only gather that something
exists of nature unknown. If philosophers choose to call things
which we do not know "ghosts," I shall not deny the existence
of such, for there are an infinity of things, which I cannot
make out.

Pray tell me, my dear Sir, before I explain myself further in
the matter, What are these ghosts or spectres? Are they
children, or fools, or madmen? For all that I have heard of
them seems more adapted to the silly than the wise, or, to say
the best we can of it, resembles the pastimes of children or of
fools. Before I end, I would submit to you one consideration,
namely, that the desire which most men have to narrate
things, not as they really happened, but as they wished them to
happen, can be illustrated from the stories of ghosts and
spectres more easily than from any others. The principal
reason for this is, I believe, that such stories are only attested
by the narrators, and thus a fabricator can add or suppress
circumstances, as seems most convenient to him, without fear
of anyone being able to contradict him. He composes them to
suit special circumstances, in order to justify the fear he feels
of dreams and phantoms, or else to confirm his courage, his
credit, or his opinion. There are other reasons, which lead me
to doubt, if not the actual stories, at least some of the narrated
circumstances; and which have a close bearing on the
conclusion we are endeavouring to derive from the aforesaid
stories. I will here stop, until I have learnt from you what those
stories are, which have so completely convinced you, that you
regard all doubt about them as absurd, &c.